The present invention relates generally to rocker arms and rocker arm assemblies in internal combustion engine drive trains.
In an internal combustion engine it is vital that all contacts and bearing surfaces be properly lubricated. If too little lubricant is supplied to these joints, the frictional forces created by their movement will not be overcome, leading to surface distress and eventual failure. Engine drive trains include rocker arms or levers and other moving parts which must be capable of rapid repetitive movement thousands of times each minute during high-speed operation.
The drive train of an internal combustion engine typically includes a number of reciprocating rocker arms or levers which operate to transmit the rotational movement of the camshaft to the reciprocal movement required to actuate the engine valves and/or fuel injectors. Lubricant, typically engine oil, may be supplied to each rocker arm from the engine oil supply in a variety of ways. Once the oil reaches the rocker arm, it is available to lubricate the rocker arm support surface and the rocker arm contact surfaces.
One method of lubricating the rocker arm components involves forming an open groove in the top of the rocker arm to channel lubricant to the joint contacting end of the rocker arm. Typical rocker arm bearings are lubricated during normal engine duty cycles by the pressurized oil traveling through pushrods and rocker arm ball socket openings. The oil pressure increases and decreases with the engine rpm. The varying engine speed and corresponding oil pressure creates a lubricating environment in the head ranging from oil traveling along the rocker arm lube rails at idle to squirting oil at higher speeds. During these higher speeds, the rocker arm working surfaces and bearings are lubricated by the oil splash. At lower speeds, the oil pressure is not sufficient to create an oil splash environment in the engine head. Certain engine applications, where these roller rocker arms are used, run at lower speeds for extended periods of time, and therefore, don't provide sufficient lubrication for the bearings.